This application relates to a method and apparatus for providing a flux regulated permanent magnet machine, wherein the stator is constructed of two separate cores.
Recently, flux regulated permanent magnet machines have been proposed. In general, these machines have outer slots formed between tooth pieces. Main stator windings are received in the slots. An inner flux diverter closes off the slots, and receives a control coil.
As shown in FIG. 1, a known permanent magnet machine 10 is provided with flux regulation and includes tooth pieces 12 defining intermediate slots or spaces 14, which receive main stator windings 16. Flux diverters 18 close off the spaces 14, and receive control coils 19. The control coils 19 control the flux at the main stator windings 16. Generally, if no control current is supplied to the control coils 19, a reluctance of the magnetic shunt provided by the flux diverters 18 is low because its magnetic permeability is high. Almost the total air gap magnetic flux produced by permanent magnets in an associated rotor 11 goes through the flux diverters 18. EMF induced in the main stator windings 16 is almost zero because the magnetic flux linked with the main stator windings 16 is very small.
If the control current is increased above zero, then the magnetic flux diverters 18 partially saturate, and their magnetic permeability decreases. Reluctance increases, and only a portion of the magnetic flux is shunted by the flux diverter 18. The magnetic flux linked with the main stator winding 16 increases, as does the EMF induced in the main stator windings 16.
A further increase in the control current further reduces the flux diverter reluctance, and its relative permeability becomes close to unity. A fully saturated flux diverter behaves as a free space, and almost the whole air gap magnetic flux excited by the rotor permanent magnets penetrates through the stator teeth 12 and excites a maximum EMF in the main stator windings 16. The benefits of such a system are known, as are the techniques for providing such control. Generally, the current in the control coils 19 is controlled to control the EMF and magnetic flux transmitted to the main stator windings 16 by the permanent magnets in the rotor 11.
However, challenges are raised to provide the stator, particularly in production quantities, given the location of the flux diverter 18 closing off the slot 14.